The growing popularity of the Internet in recent years has made technology that increases the communications bandwidth more important, leading to a rise in the use of optical fiber networks. The coupling technology most commonly used today for the assembly of optical materials and optical components employed in such optical communications systems involves the use of connectors to connect one optical fiber to another. Adhesive compositions for securing the optical fibers to the ferrule within such a connector are required to have a high adhesive strength and reliability. In particular, when the optical fibers are bonded to a connector with an adhesive, because the optical fibers are always in a mutually pressure-bonded state under the action of a spring, the adhesive between the optical fibers and the ferrule constantly incurs shear stress. Moreover, the optical fibers are sometimes pulled in the lengthwise direction of the ferrules and subjected to large loads. The adhesive is thus required to have a high shear strength.
Moreover, because optical fibers are sometimes installed outdoors or in an attic, for example, the adhesive is also required to be capable of maintaining a sufficient bond strength even in a harsh environment, such as at high temperature and high humidity.
Quartz and glass have hitherto been used as optical fiber materials. However, plastic optical fibers (POF) have been developed which are low-cost, easy to work, and have a good flex strength, preventing the fibers from breaking easily. Such plastic optical fibers are being used in short-range communications applications, such as home networks and digital consumer electronics. Hence, adhesive compositions for optical fibers are required to be capable of bonding not only to glass, but also to plastic (primarily acrylic plastic).
Up until now, epoxy-based adhesives and the like have been used as adhesive compositions for optical fibers. However, recent research has shown there to be problems with the durability of epoxy adhesives. Also, the fact that epoxy adhesives must be heated to about 110° C. to cure complicates the work done at the site where connection is actually carried out. In addition, the use of epoxy adhesives may cause health problems such as rashes.
Patent Document 1 discloses an adhesive composition composed primarily of polysiloxane which is intended to provide excellent heat resistance, reduce bubble formation during curing, and eliminate defects such as clouding due to bubbles and the like.    Patent Document 1: JP 2002-173661 A